Hydrogen detection method and device based on low-frequency quartz crystal oscillator

Abstract

The invention discloses a hydrogen detection method and device based on a low-frequency quartz crystal oscillator. The method comprises the following steps: S1, introducing gas to be detected into a gas chamber with the quartz crystal oscillator; s2, the signal generator provides sinusoidal voltage excitation for the quartz crystal oscillator, and the quartz crystal oscillator detects a generated voltage signal through the sinusoidal voltage excitation; and S3, analyzing the voltage signal detected by the quartz crystal oscillator, and calculating the concentration of hydrogen in the gas to be detected. According to the technical scheme, the low-frequency quartz crystal oscillator is electrically excited to monitor the resonance characteristic of the quartz crystal oscillator to detect the hydrogen concentration, a laser light source does not need to be used, the device has the anti-electromagnetic interference capacity and is low in cost, and high-sensitivity detection can be achieved in the high-concentration or low-concentration large-dynamic-range hydrogen environment.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen detection, and in particular to a hydrogen detection method and device based on a low-frequency quartz crystal oscillator. Background Art

[0002] As a clean, efficient and universal sustainable energy source, hydrogen has attracted extensive attention from the scientific community. Hydrogen sensing technology plays a vital role in the entire process of hydrogen production, storage, transportation and use. At present, the technologies used in hydrogen detection mainly include electrical sensors and optical detection technologies.

[0003] The types of electrical sensors include thermal conductivity sensors, catalytic sensors, semiconductor metal oxide resistor sensors and electrochemical sensors. For example, the "Hydrogen sensor and its manufacturing method" published in the publication number CN 118465002A and the "Multilayer palladium-based microthermal hydrogen sensor based on MEMS technology and its preparation method" published in the publication number CN 118671149A. Although electrical sensors are widely used, they are easily affected by strong electromagnetic interference. Due to the limitation of hydrogen concentration, hydrogen is highly flammable at high concentrations. Sparks may be generated due to the mixture inside the sensor under high concentration conditions. The explosion limit of hydrogen is 4%, which may lead to uncontrollable explosion risks.

[0004] Optical detection technologies include hydride-based optical sensors and tunable diode laser absorption spectroscopy (TDLAS) sensors, such as the "A hydrogen-sensitive optical element and hydrogen-sensitive optical sensor" published in publication number CN 215894363U. In contrast, optical detection technology can overcome the problem of electromagnetic interference, but it also has certain limitations. Hydride-based optical sensors have a short lifespan, slow response speed, long recovery time, low stability, and are easily affected by humidity. In addition, this type of sensor is not suitable for use in a high-concentration hydrogen environment.

[0005] On the other hand, the absorption line of hydrogen in the infrared region is very sparse and weak, which makes the TDLAS sensor extremely demanding in the selection of laser source. From the spectrum database HITRAN, it can be calculated that the strongest absorption line of hydrogen is at 2122nm (4712.9cm -1 ) is 3.189×10 -26 cm / molecule, which is located at 2606nm (3837.87cm -1 ) at 2.479×10 -19The absorption line strength of cm / molecule differs by 7 orders of magnitude, which results in low sensitivity of laser detection sensors such as TDLAS for hydrogen. Although the problem of weak absorption cross section can be compensated by long absorption path or multi-pass cell, it also increases the complexity of noise processing.

[0006] In view of this, this application is hereby filed. Summary of the invention

[0007] The technical problem to be solved by the present invention is that the existing hydrogen sensors are susceptible to electromagnetic interference, are limited by hydrogen concentration, are not suitable for use in high-concentration hydrogen environments, and have too strict requirements on laser sources. The purpose is to provide a hydrogen detection method and device based on a low-frequency quartz crystal oscillator, which detects the hydrogen concentration by electrically exciting the low-frequency quartz crystal oscillator to monitor the resonance characteristics of the quartz crystal oscillator. It does not require the use of a laser light source, has anti-electromagnetic interference capability, is low in cost, and can achieve high-sensitivity detection in a high-concentration or low-concentration hydrogen environment with a large dynamic range.

[0008] The present invention is achieved through the following technical solutions:

[0009] In a first aspect, the present invention provides a hydrogen detection method based on a low-frequency quartz crystal oscillator, comprising the following steps:

[0010] S1, passing the gas to be tested into the gas chamber equipped with a quartz crystal oscillator;

[0011] S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator, and the quartz crystal oscillator detects the voltage signal generated by the sinusoidal voltage excitation;

[0012] S3, by analyzing the voltage signal detected by the quartz crystal oscillator, the concentration of hydrogen in the gas to be tested is calculated.

[0013] In a specific implementation, in step S1, the flow rate and pressure of the gas to be tested in the gas chamber are kept constant to ensure stable test conditions.

[0014] In a specific implementation, in step S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator and sends a synchronization signal to a phase-locked amplifier as a reference signal, and the voltage signal detected by the quartz crystal oscillator is input into the phase-locked amplifier for demodulation and analysis.

[0015] In a specific implementation, in step S3, the resonant frequency f or the quality factor Q of the quartz crystal in the gas to be measured is analyzed by collecting signals to calculate the hydrogen mole fraction x in the gas to be measured, thereby calculating the concentration of hydrogen in the gas to be measured.

[0016] In a specific embodiment, the resonant frequency of the quartz crystal in the gas to be measured is Where Δt is the time interval between two consecutive peaks, f B is the modulation frequency of the quartz crystal oscillator, and Δf is the detuning of the modulation frequency of the quartz crystal oscillator relative to the resonance frequency f.

[0017] The present invention adopts a technical solution of measuring the resonance characteristics of an electrically excited low-frequency quartz crystal oscillator to realize the concentration detection of hydrogen. Since the quartz crystal oscillator has dielectric properties, the system can effectively resist electromagnetic interference; at the same time, the quartz crystal oscillator can be excited by a weak electric field, and the risk of sparks in the mixture can be ignored, so the gas to be tested with a high concentration of hydrogen can be effectively detected; at the same time, the present invention does not need to use a laser source, effectively reducing the system cost, and overcoming the disadvantage that the existing hydrogen spectrum sensing technology has very strict requirements on the laser source.

[0018] In a specific embodiment, using the exponential law e -t / τ Each peak time coordinate of the collected signal wave is fitted, and the quality factor Q is obtained according to the formula quality factor Q=πτf using the τ and τ obtained by fitting.

[0019] In a specific embodiment, the calculation relationship between the resonance frequency f and the hydrogen mole fraction x in step S3 is as follows:

[0020] The resonant frequency of a quartz crystal immersed in a gas medium is affected by the gas medium, that is, the additional inertia or additional mass of the vibration. The resonant frequency f is expressed as:

[0021]

[0022] Where ρ is the density of quartz, A is the cross-sectional area of ​​the quartz crystal oscillator arm, u is the additional mass, and f0 is u=0, which represents the resonant frequency under vacuum conditions;

[0023] Among them, the resonance frequency decreases linearly with the increase of the additional mass, and the additional mass u is related to the gas density ρ gas Proportional, expressed as:

[0024]

[0025] Since the additional mass u and the gas density ρ gas Proportional, combined with equation (1) and equation (2), the resonant frequency f is linearly related to the gas medium pressure P, expressed as:

[0026] f=f0-kP Formula (3);

[0027] In the formula, k depends on the molar mass of the mixture;

[0028] When the quartz crystal is in a mixture containing a hydrogen mole fraction x and the remaining nitrogen, the effective molar mass M of the mixture is effIt is the molar mass of hydrogen and nitrogen in the mixture multiplied by their relative amounts, expressed as:

[0029]

[0030] In the formula, denote the molar masses of hydrogen and nitrogen respectively;

[0031] Combining equations (3) and (4), because As long as the mixed gas pressure is kept constant, the resonance frequency has a positive linear relationship with the hydrogen mole fraction x.

[0032] In a specific embodiment, the calculation relationship between the quality factor Q and the hydrogen mole fraction x in step S3 is as follows:

[0033] The quality factor Q of a quartz crystal represents the energy efficiency and is related to the dissipation mechanism, of which viscous damping is the main factor in a gas environment. The quality factor Q is expressed as the sum of two contributions:

[0034]

[0035] In the formula, Q gas Relevant only to gas damping, Q0 includes all other loss mechanisms that are not affected by the surrounding gas medium;

[0036] According to the Hosaka model, Q gas It is expressed as:

[0037]

[0038] Where μ is the gas viscosity, w is the arm width of the quartz crystal oscillator, and the gas density ρ is gas According to formula (2), it is related to pressure, so the quality factor Q is related to the pressure and viscosity of the surrounding gas medium;

[0039] Combining equations (5) and (6), the relationship between the quality factor Q and the pressure P is expressed as:

[0040]

[0041] In the formula,

[0042]

[0043] For the quality factor Q, combined with formula (7-9), it is related to the gas viscosity μ; for the viscosity and The ideal binary mixture, i.e., each component does not produce any volume change, has a dynamic effective viscosity μ eff Following the Arrhenius equation, it is expressed as:

[0044]

[0045] From the above formula, we can derive mathematically:

[0046]

[0047] because The exponent is negative, and the domain of x is [0,1], so equation (11) can be linearly approximated by the first order:

[0048]

[0049] Combining equations (7-9) with equations (4) and (11), we only emphasize the effective molar mass M eff and effective dynamic viscosity μ eff , that is, all other multiplicative parameters are normalized to constants, then the trend of the quality factor Q as a function of the hydrogen mole fraction x is expressed as:

[0050]

[0051] In the above formula, C and D are constants, and there is a first-order approximation:

[0052]

[0053] Combining equations (13) and (14), the trend of 1 / Q as a function of hydrogen mole fraction x is linearized with a negative slope.

[0054] As shown above, the two resonance parameters, namely the resonance frequency f and the quality factor Q, are linearly related to the hydrogen mole fraction x, and the mole fraction also represents the hydrogen concentration information. Therefore, the present invention can analyze the hydrogen mole fraction x in the gas to be measured by analyzing the resonance frequency f or the quality factor Q of the gas to be measured, and then calculate the hydrogen concentration information in the gas to be measured.

[0055] In a second aspect, the present invention provides a hydrogen detection device based on a low-frequency quartz crystal oscillator, comprising a signal generator, a gas chamber, a quartz crystal oscillator, a phase-locked amplifier, a data acquisition module and a data analysis module;

[0056] A quartz crystal oscillator is arranged in the air chamber, and the air chamber is also provided with an air inlet and an air outlet for the gas to be measured to enter and discharge;

[0057] The signal generator is used to provide a sinusoidal voltage excitation to the quartz crystal oscillator in the gas chamber and a synchronization signal to the phase-locked amplifier;

[0058] The lock-in amplifier performs signal demodulation on the voltage signal detected by the input quartz crystal oscillator according to the reference signal output by the signal generator;

[0059] The data acquisition module is used to adopt the demodulated signal of the lock-in amplifier and output it to the data analysis module;

[0060] The data analysis module performs data analysis and processing to calculate the concentration information of hydrogen in the gas to be tested.

[0061] In a specific embodiment, a mass flow controller is installed at the air inlet, and an air pump is connected to the air outlet through a needle valve;

[0062] Used to adjust the flow rate and pressure of the gas to be measured in the control chamber.

[0063] The gas to be tested enters the gas chamber from the air inlet through the mass flow controller, and then is discharged from the air outlet through the needle valve and air pump. The mass flow controller, needle valve and air pump jointly control the flow rate and pressure of the gas in the gas chamber to ensure stable test conditions.

[0064] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0065] 1. A hydrogen detection method and device based on a low-frequency quartz crystal oscillator provided in an embodiment of the present invention realizes hydrogen concentration detection by adopting a technical solution of measuring the resonance characteristics by electrically exciting a low-frequency quartz crystal oscillator, has anti-electromagnetic interference, and can realize high-sensitivity detection in a high-concentration or low-concentration hydrogen environment with a large dynamic range;

[0066] 2. A hydrogen detection method and device based on a low-frequency quartz crystal oscillator provided in an embodiment of the present invention, wherein the adopted quartz crystal oscillator has dielectric properties and can effectively resist electromagnetic interference;

[0067] 3. A method and device for detecting hydrogen based on a low-frequency quartz crystal oscillator provided in an embodiment of the present invention. The quartz crystal oscillator can be excited by a weak electric field, and the risk of sparks in the mixture can be ignored, so that the system can effectively detect the gas to be tested with a high concentration of hydrogen;

[0068] 4. The embodiment of the present invention provides a hydrogen detection method and device based on a low-frequency quartz crystal oscillator, which does not require a laser source, effectively reduces system costs, and overcomes the disadvantage that the existing hydrogen spectrum sensing technology has very strict requirements on the laser source. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0070] Figure 1 A diagram of a hydrogen detection device based on a low-frequency quartz crystal oscillator provided in an embodiment of the present invention;

[0071] Figure 2 A linear relationship diagram between the resonance frequency f and the hydrogen mole fraction x provided in an embodiment of the present invention;

[0072] Figure 3 A linear relationship diagram between the quality factor Q and the hydrogen mole fraction x provided in an embodiment of the present invention.

[0073] Reference numerals and corresponding parts names:

[0074] 1-signal generator, 2-gas chamber, 3-air inlet, 4-air outlet, 5-phase-locked amplifier, 6-data acquisition module, 7-data analysis module, 8-gas to be tested, 9-mass flow controller, 10-needle valve, 11-air pump. DETAILED DESCRIPTION

[0075] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0076] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is apparent to those of ordinary skill in the art that these specific details do not have to be employed to practice the present invention. In other embodiments, in order to avoid confusing the present invention, well-known structures are not specifically described.

[0077] Throughout the specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment," "an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. In addition, it will be appreciated by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0078] In the description of the present invention, the directions or positional relationships indicated by terms such as “front”, “rear”, “left”, “right”, “up”, “down”, “vertical”, “horizontal”, “high”, “low”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the scope of protection of the present invention.

[0079] Example 1

[0080] The embodiment of the present invention provides a hydrogen detection method based on a low-frequency quartz crystal oscillator, comprising the following steps:

[0081] S1, passing the gas to be tested into the gas chamber equipped with a quartz crystal oscillator;

[0082] S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator, and the quartz crystal oscillator detects the voltage signal generated by the sinusoidal voltage excitation;

[0083] S3, by analyzing the voltage signal detected by the quartz crystal oscillator, the concentration of hydrogen in the gas to be tested is calculated.

[0084] In a specific implementation, in step S1, the flow rate and pressure of the gas to be measured in the gas chamber are kept constant.

[0085] In a specific implementation, in step S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator and sends a synchronization signal to a phase-locked amplifier as a reference signal, and the voltage signal detected by the quartz crystal oscillator is input into the phase-locked amplifier for demodulation and analysis.

[0086] In a specific implementation, in step S3, the resonant frequency f or the quality factor Q of the quartz crystal in the gas to be measured is analyzed by collecting signals to calculate the hydrogen mole fraction x in the gas to be measured, thereby calculating the concentration of hydrogen in the gas to be measured.

[0087] In a specific embodiment, the resonant frequency of the quartz crystal in the gas to be measured is Where Δt is the time interval between two consecutive peaks, f B is the modulation frequency of the quartz crystal oscillator, and Δf is the detuning of the modulation frequency of the quartz crystal oscillator relative to the resonance frequency f.

[0088] The present invention adopts a technical solution of measuring the resonance characteristics of an electrically excited low-frequency quartz crystal oscillator to realize the concentration detection of hydrogen. Since the quartz crystal oscillator has dielectric properties, the system can effectively resist electromagnetic interference; at the same time, the quartz crystal oscillator can be excited by a weak electric field, and the risk of sparks in the mixture can be ignored, so the gas to be tested with a high concentration of hydrogen can be effectively detected; at the same time, the present invention does not need to use a laser source, effectively reducing the system cost, and overcoming the disadvantage that the existing hydrogen spectrum sensing technology has very strict requirements on the laser source.

[0089] In a specific embodiment, using the exponential law e -t / τ Each peak time coordinate of the collected signal wave is fitted, and the quality factor Q is obtained according to the formula quality factor Q=πτf using the τ and τ obtained by fitting.

[0090] In a specific embodiment, the calculation relationship between the resonance frequency f and the hydrogen mole fraction x in step S3 is as follows:

[0091] The resonant frequency of a quartz crystal immersed in a gas medium is affected by the gas medium, that is, the additional inertia or additional mass of the vibration. The resonant frequency f is expressed as:

[0092]

[0093] Where ρ is the density of quartz, A is the cross-sectional area of ​​the quartz crystal oscillator arm, u is the additional mass, and f0 is u=0, which represents the resonant frequency under vacuum conditions;

[0094] Among them, the resonance frequency decreases linearly with the increase of the additional mass, and the additional mass u is related to the gas density ρ gas Proportional, expressed as:

[0095]

[0096] Since the additional mass u and the gas density ρ gas Proportional, combined with equation (1) and equation (2), the resonant frequency f is linearly related to the gas medium pressure P, expressed as:

[0097] f=f0-kP Formula (3);

[0098] In the formula, k depends on the molar mass of the mixture;

[0099] When the quartz crystal is in a mixture containing a hydrogen mole fraction x and the remaining nitrogen, the effective molar mass M of the mixture is eff It is the molar mass of hydrogen and nitrogen in the mixture multiplied by their relative amounts, expressed as:

[0100]

[0101] In the formula, denote the molar masses of hydrogen and nitrogen respectively;

[0102] Combining equations (3) and (4), because As long as the mixed gas pressure is kept constant, the resonance frequency has a positive slope linear relationship with the hydrogen mole fraction x, such as Figure 2 shown.

[0103] In a specific embodiment, the calculation relationship between the quality factor Q and the hydrogen mole fraction x in step S3 is as follows:

[0104] The quality factor Q of a quartz crystal represents the energy efficiency and is related to the dissipation mechanism, of which viscous damping is the main factor in a gas environment. The quality factor Q is expressed as the sum of two contributions:

[0105]

[0106] In the formula, Q gas Relevant only to gas damping, Q0 includes all other loss mechanisms that are not affected by the surrounding gas medium;

[0107] According to the Hosaka model, Q gas It is expressed as:

[0108]

[0109] Where μ is the gas viscosity, w is the arm width of the quartz crystal oscillator, and the gas density ρ is gas According to formula (2), it is related to pressure, so the quality factor Q is related to the pressure and viscosity of the surrounding gas medium;

[0110] Combining equations (5) and (6), the relationship between the quality factor Q and the pressure P is expressed as:

[0111]

[0112] In the formula,

[0113]

[0114] For the quality factor Q, combined with formula (7-9), it is related to the gas viscosity μ; for the viscosity and The ideal binary mixture, i.e., each component does not produce any volume change, has a dynamic effective viscosity μ eff Following the Arrhenius equation, it is expressed as:

[0115]

[0116] From the above formula, we can derive mathematically:

[0117]

[0118] because The exponent is negative, and the domain of x is [0,1], so equation (11) can be linearly approximated by the first order:

[0119]

[0120] Combining equations (7-9) with equations (4) and (11), we only emphasize the effective molar mass M eff and effective dynamic viscosity μ eff , that is, all other multiplicative parameters are normalized to constants, then the trend of the quality factor Q as a function of the hydrogen mole fraction x is expressed as:

[0121]

[0122] In the above formula, C and D are constants, and there is a first-order approximation:

[0123]

[0124] Combining equations (13) and (14), the trend of 1 / Q as a function of hydrogen mole fraction x is linearized with a negative slope, as shown in Figure 3 shown.

[0125] As shown above, the two resonance parameters, namely the resonance frequency f and the quality factor Q, are linearly related to the hydrogen mole fraction x, and the mole fraction also represents the hydrogen concentration information. Therefore, the present invention can analyze the hydrogen mole fraction x in the gas to be measured by analyzing the resonance frequency f or the quality factor Q of the gas to be measured, and then calculate the hydrogen concentration information in the gas to be measured.

[0126] Example 2

[0127] like Figure 1 As shown, an embodiment of the present invention provides a hydrogen detection device based on a low-frequency quartz crystal oscillator, comprising a signal generator 1, a gas chamber 2, a quartz crystal oscillator, a phase-locked amplifier 5, a data acquisition module 6 and a data analysis module 7;

[0128] A quartz crystal oscillator is arranged in the air chamber 2, and the air chamber 2 is also provided with an air inlet 3 and an air outlet 4 for the gas 8 to be measured to enter and discharge;

[0129] The signal generator 1 is used to provide a sinusoidal voltage excitation to the quartz crystal oscillator in the air chamber 2 and a synchronization signal to the phase-locked amplifier 5;

[0130] The lock-in amplifier 5 performs signal demodulation on the voltage signal detected by the input quartz crystal oscillator according to the reference signal output by the signal generator 1;

[0131] The data acquisition module is used to use the demodulated signal of the lock-in amplifier 5 and output it to the data analysis module 7;

[0132] The data analysis module 7 performs data analysis and processing to calculate the concentration information of hydrogen in the gas to be measured 8.

[0133] In a specific embodiment, a mass flow controller 9 is installed at the air inlet 3, and an air pump 11 is connected to the air outlet 4 through a needle valve 10, which is used to adjust the flow rate and pressure of the gas to be measured in the control chamber.

[0134] In the detection device of the present invention, the gas to be tested 8 enters the gas chamber 2 equipped with a quartz crystal oscillator from the gas inlet 3 through the mass flow controller 9, and is discharged from the gas outlet 4 by the air pump 11 through the needle valve 10. Among them, the air pump 11 continuously draws gas at the gas outlet end, sets the flow rate of the mass flow controller 9 to complete the flow rate control of the gas to be tested, and adjusts the needle valve 10 to read the pressure reading on the mass flow controller 9 at the same time to complete the pressure control of the gas to be tested in the gas chamber 2 equipped with a quartz crystal oscillator.

[0135] After completing the control of the flow rate and pressure of the gas to be measured in the gas chamber 2 equipped with the quartz crystal oscillator, the signal generator 1 is used to output a sinusoidal signal to the quartz crystal oscillator to provide it with a sinusoidal voltage excitation, and the signal is synchronized to the phase-locked amplifier 5 as a reference signal for demodulation. Among them, the sinusoidal signal is the modulation frequency f of the quartz crystal oscillator. B The quartz crystal is detuned by Δf relative to the resonant frequency f, and the sine wave excitation is turned off after about 0.1s, and is excited periodically. When the sine wave pulse is completed, the quartz crystal will relax and oscillate at its resonant frequency.

[0136] Next, the voltage signal detected by the quartz crystal oscillator is input to the lock-in amplifier 5, which demodulates the signal according to the reference signal output by the signal generator 1. B If the demodulated quartz crystal signal is at Δf, the locked output in the time domain will appear as a damped sine waveform at Δf.

[0137] Finally, the demodulated signal of the lock-in amplifier 5 is collected by the data acquisition module 6 and output to the data analysis module 7, such as a local computer, which analyzes and processes the data to invert the concentration information of hydrogen in the gas to be measured 8. The local computer 7 uses the exponential law e -t / τ Fit each peak time coordinate collected, use the fitted τ and the estimated time interval Δt between two consecutive peaks, and according to the formula quality factor Q = πτf and its resonance frequency Obtain the resonant frequency f or quality factor Q, and compare these two resonance parameters with the linear relationship between the resonant frequency f or quality factor Q and the hydrogen mole fraction x in the standard gas. The linear relationship between the resonant frequency f and the quality factor Q and the hydrogen mole fraction x is as follows: Figure 2 and Figure 3 As shown, the hydrogen mole fraction x in the gas to be measured 8 is obtained, thereby further inverting the hydrogen concentration information in the gas to be measured 8.

[0138] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hydrogen detection method based on low-frequency quartz crystal oscillator, characterized in that: The steps include: S1, passing the gas to be tested into the gas chamber equipped with a quartz crystal oscillator; S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator, and the quartz crystal oscillator detects the voltage signal generated by the sinusoidal voltage excitation; S3, by analyzing the voltage signal detected by the quartz crystal oscillator, the concentration of hydrogen in the gas to be tested is calculated.

2. The hydrogen detection method based on a low-frequency quartz crystal oscillator according to claim 1 is characterized in that: In step S1, the flow rate and pressure of the gas to be measured in the gas chamber are kept constant.

3. The hydrogen detection method based on a low-frequency quartz crystal oscillator according to claim 1, characterized in that: In step S2, the signal generator provides a sinusoidal voltage excitation to the quartz crystal oscillator and sends a synchronization signal to the phase-locked amplifier as a reference signal. The voltage signal detected by the quartz crystal oscillator is input into the phase-locked amplifier for demodulation and analysis.

4. The hydrogen detection method based on low-frequency quartz crystal oscillator according to claim 1 is characterized in that: In step S3, the resonant frequency f or the quality factor Q of the quartz crystal in the gas to be measured is analyzed by collecting signals, and the mole fraction x of hydrogen in the gas to be measured is calculated, thereby calculating the concentration of hydrogen in the gas to be measured.

5. A hydrogen detection method based on a low-frequency quartz crystal oscillator according to claim 4, characterized in that: The resonant frequency of the quartz crystal in the gas to be measured Where Δt is the time interval between two consecutive peaks, f B is the modulation frequency of the quartz crystal oscillator, and Δf is the detuning of the modulation frequency of the quartz crystal oscillator relative to the resonance frequency f.

6. A hydrogen detection method based on a low-frequency quartz crystal oscillator according to claim 5, characterized in that: Using the exponential law -t / τ Each peak time coordinate of the collected signal wave is fitted, and the quality factor Q is obtained according to the formula quality factor Q=πτf using the τ and τ obtained by fitting.

7. A hydrogen detection method based on a low-frequency quartz crystal oscillator according to claim 4, characterized in that: In step S3, the calculation relationship between the resonance frequency f and the hydrogen mole fraction x is as follows: The resonant frequency of a quartz crystal immersed in a gas medium is affected by the gas medium, that is, the additional mass of the vibration. The resonant frequency f is expressed as: Where ρ is the density of quartz, A is the cross-sectional area of ​​the quartz crystal oscillator arm, u is the additional mass, and f0 is u=0, which represents the resonant frequency under vacuum conditions; Among them, the additional mass u and the gas density ρ gas Proportional, expressed as: Since the additional mass u and the gas density ρ gas Proportional, combined with equation (1) and equation (2), the resonant frequency f is linearly related to the gas medium pressure P, expressed as: f=f0-kP Formula (3); In the formula, k depends on the molar mass of the mixture; When the quartz crystal is in a mixture containing a hydrogen mole fraction x and the remaining nitrogen, the effective molar mass M of the mixture is eff It is the molar mass of hydrogen and nitrogen in the mixture multiplied by their relative amounts, expressed as: In the formula, denote the molar masses of hydrogen and nitrogen respectively; Combining equations (3) and (4), because As long as the mixed gas pressure is kept constant, the resonance frequency has a positive linear relationship with the hydrogen mole fraction x.

8. The hydrogen detection method based on low-frequency quartz crystal oscillator according to claim 7 is characterized in that: In step S3, the calculation relationship between the quality factor Q and the hydrogen mole fraction x is as follows: The quality factor Q of a quartz crystal represents the energy efficiency and is related to the dissipation mechanism, of which viscous damping is the main factor in a gas environment. The quality factor Q is expressed as: In the formula, Q gas Relevant only to gas damping, Q0 includes all other loss mechanisms that are not affected by the surrounding gas medium; According to the Hosaka model, Q gas It is expressed as: Where μ is the gas viscosity, w is the arm width of the quartz crystal oscillator, and the gas density ρ is gas According to formula (2), it is related to pressure, so the quality factor Q is related to the pressure and viscosity of the surrounding gas medium; Combining equations (5) and (6), the relationship between the quality factor Q and the pressure P is expressed as: In the formula, Combining formula (7-9), for the viscosity and The dynamic effective viscosity μ of a binary ideal mixture is eff Following the Arrhenius equation, it is expressed as: From the above formula, we can derive mathematically: because The exponent is negative, and the domain of x is [0,1], so equation (11) can be linearly approximated by the first order: Combining equations (7-9) with equations (4) and (11), we only emphasize the effective molar mass M eff and effective dynamic viscosity μ eff , that is, all other multiplicative parameters are normalized to constants, then the trend of the quality factor Q as a function of the hydrogen mole fraction x is expressed as: In the formula, C and D are constants, and there is a first-order approximation: The 1 / Q trend is linearized with a negative slope. Combining equations (13) and (14), the trend of 1 / Q as a function of hydrogen mole fraction x is linearized with a negative slope.

9. A hydrogen detection device based on a low-frequency quartz crystal oscillator for executing the detection method according to any one of claims 1 to 8, characterized in that: It comprises a signal generator (1), an air chamber (2), a quartz crystal oscillator, a phase-locked amplifier (5), a data acquisition module (6) and a data analysis module (7); A quartz crystal oscillator is arranged in the air chamber (2), and the air chamber (2) is also provided with an air inlet (3) and an air outlet (4) for the gas to be measured (8) to enter and discharge; The signal generator (1) is used to provide a sinusoidal voltage excitation to the quartz crystal oscillator in the gas chamber (2) and to transmit a synchronization signal to a phase-locked amplifier (5); The phase-locked amplifier (5) performs signal demodulation on the voltage signal detected by the input quartz crystal oscillator according to the reference signal output by the signal generator (1); The data acquisition module is used to use the demodulated signal of the lock-in amplifier (5) and output it to the data analysis module (7); The data analysis module (7) performs data analysis and processing to calculate the concentration information of hydrogen in the gas to be tested (8).

10. A hydrogen detection device based on a low-frequency quartz crystal oscillator according to claim 9, characterized in that: A mass flow controller (9) is installed at the air inlet (3), and an air pump (11) is connected to the air outlet (4) via a needle valve (10); Used to adjust the flow rate and pressure of the gas to be measured in the control chamber.

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